Japanese Patent Laying-Open No. 2002-10502 discloses a charging and discharging device for storage batteries that charges and discharges a plurality of storage batteries simultaneously. This charging and discharging device for storage batteries includes a rectifying circuit for charging that rectifies an alternating current (AC) power supply, a rectifying circuit for regeneration that is in antiparallel to this rectifying circuit for charging and regenerates the amount of electricity of the storage batteries to the AC power supply, a step-up/down converter having a switching element that is at an output of the rectifying circuit for charging and controls an output, a smoothing capacitor smoothing an output of the step-up/down converter, a first voltage detector detecting a voltage across the smoothing capacitor, and a second voltage detector detecting a storage battery voltage of the storage batteries. The step-up/down converter is controlled such that a detection signal of the first voltage detector becomes a detection signal of the second voltage detector.
By thus controlling the step-up/down converter, the provision of a current-limiting resistor of a large capacity that limits an inrush current at the start of discharging and also a current-limiting resistor as well as opening and closing means is no longer required.
In recent years, electric vehicles whose wheels are driven by a motor, fuel cell vehicles and hybrid vehicles powered by both a motor and an engine have received attention as environmentally-friendly vehicles. In these vehicles, a voltage source such as a storage battery is stepped up by a step-up/down converter and the stepped up voltage is supplied to an inverter for driving a motor.
Furthermore, in these vehicles, it is considered to mount a plurality of power storage devices in order to realize both fuel efficiency and dynamics as well as to extend the distance traveled by the vehicles without being refueled. In a power supply apparatus for a vehicle, where the plurality of power storage devices are mounted, a current-limiting resistor of a large capacity that limits an inrush current at the start of discharging also needs to be provided. Furthermore, a current-limiting resistor as well as opening and closing means also need to be provided for each power storage device.
The above-described Japanese Patent Laying-Open No. 2002-10502 is directed to a device connected to a three-phase AC power supply that is a commercial power supply, and relates to a device that carries out a charging and discharging test of the storage batteries. Since energy is supplied from the three-phase AC power supply that is a commercial power supply capable of supplying electric power as needed to a step-up converter, the step-up/down converter can be readily controlled in order to reduce a voltage difference at the time of discharging before the step-up converter is connected to the storage batteries.
In the vehicle when a power supply system stops (in the case of a hybrid vehicle, when an engine also stops), however, a relay is opened and the power storage device is separated from the step-up/down converter. Here, since there is no other voltage source at the step-up/down converter, additional measures are required to operate the step-up/down converter. In other words, the technology for the charging and discharging test device using the commercial power supply is not applicable to the power supply apparatus for a vehicle as it is.